Various types of surgeries utilize precision instrumentation and robotics. Despite significant advancements, such instrumentation presents challenges, especially as applied to the use of surgical tools in delicate, or generally difficult, operations. For example, it has been shown that certain aspects of traditional retinal microsurgery procedures are at or beyond the limits of human precision. In some examples of traditional retinal microsurgery, an error of only a few micrometers can cause a surgical instrument to exert damaging force on the retina, causing localized loss of vision, increased chances of infection, or other complications. The forces experienced during retinal surgeries can be below what surgeons can feel (<7 mN), and, therefore, surgeons must rely on visual feedback only. The surgeon pivots the instruments about the scleral trocars, limiting dexterity, and uses the instruments to manipulate the eye to provide better imaging through a corresponding surgical microscope. Patient movement due to breathing must also be accounted for by the surgeon, and in addition, among patients who snore under monitored anesthesia (indicated to be in ≈16% of cases), half have sudden head movements during surgery, leading to a high risk of complications.
One of the most difficult retinal-surgery procedures involves the peeling of membranes on the retina. Epiretinal membrane (ERM) comprises sheets of fibrous tissue up to 61-μm thick that can distort macular anatomy and disturb vision after posterior vitreous detachment or retinal tears, and the inner limiting membrane (ILM) is a naturally occurring 0.15-4-μm thick membrane that can contract with age and generate macular holes. To improve vision in affected eyes, ERM and ILM are peeled by inserting delicate instruments inside the eye. Membrane peeling is a delicate procedure, and complications can occur in the form of intraoperative hemorrhage, retinal detachment during or after surgery, infection after surgery, regrowth of epiretinal membrane, and increased rate of cataract development. In some cases, a second surgery is required to remove fragments of the ERM/ILM left behind. Other experimental procedures inside the eye like retinal vein cannulation involve delivering drugs to retinal veins that measure less than 100 μm in diameter, whereas physiological tremor in the human hand during retinal surgery was measured to be 100 μm. In such surgeries, instruments are inserted through the trocars in the pars plana region of the sclera and are used to perform delicate scraping and peeling motions to peel membranes on the retina.
There are opportunities for significant improvement in retinal-surgery procedures in terms of safety and consistency of outcomes. As our population ages over coming years, the number of surgical procedures will likely increase relative to the number of surgeons available. Robot-assisted retinal surgery will enable surgeons to improve surgical efficiency by enabling them to overcome their human limitations, extend their working life, and capitalize on their experience even after their manual dexterity abilities have diminished.
Prior research in robot-assisted retinal surgery has resulted in the development of telemanipulated systems and cooperative manipulators. Robotic systems for retinal surgery have typically been relatively large and stiff, and thus table-mounted. In related work, active hand-held instruments primarily aimed at tremor reduction, with no ability to affect the “DC” system response, have been shown to reduce RMS tremor to 10 μm-60 μm. Since the human hand is the source of tremor during microsurgery, telemanipulated systems, which eliminate direct contact between the surgeon and the instrument, seem particularly promising. Most prior systems can leave the retina at risk in the event of sudden head movement, and rhythmic head movements would need to be actively compensated. Notable exceptions are the TU Munich and Columbia/Vanderbilt systems, which are designed to be patient head-mountable. The TU Munich system has been demonstrated to be head-mountable.